Electric current is the rate of flow of charge. In a metal wire the charge that moves is carried by electrons. For charge to flow you need two things: a source of potential difference, such as a cell or battery, and a closed circuit. A gap in the circuit, such as an open switch, stops the flow.
In a single closed loop the current has the same value at every point. Charge is not used up as it goes round, so an ammeter reads the same before a lamp as it does after it.
The amount of charge that passes a point depends on the current and on how long it flows. Quantity of charge is measured in coulombs (C), current in amperes (A) and time in seconds (s):
charge = current × time, or Q = I t
For example, a current of 2 A that flows for 25 s moves 2 × 25 = 50 C of charge. Always change minutes into seconds before you calculate, so 2 minutes is 120 s.